The radiological system additionally comprises a source of ionizing radiation, for example an x-ray tube, which makes it possible to generate radiation X, and a base station comprising a data processing system which makes it possible to synchronize the x-ray tube and the detector, and also makes it possible to carry out image processing, such as presenting the operator with the image which is corrected of all the faults which are inherent in the detector, and is improved for example by contour enhancement processing. An object, the image X of which is to be obtained, is placed between the source and the detector. A system of this type can be used in many applications, such as, for example, medical radiology and non-destructive testing. The invention can also be implemented for other types of radiation to be detected, notably gamma radiation.
In the past, the radiological systems were voluminous and difficult to move. It was necessary to position the object relative to the system in order to obtain the desired image. With the appearance of solid-state detectors, as described for example in French patent application FR 2 605 166, the detector became less voluminous, and it became possible to displace the detector relative to an object which remained fixed. For medical radiology, digital detectors were produced in the form of mobile cassettes, which it became possible to place in the immediate vicinity of a patient of whom an image was to be produced, when the state of health of the patient prevented him from being moved to a room reserved for radiology.
The mobile cassette essentially comprises a digital ionizing radiation detector in the form of a flat panel, and an electronic board, which notably ensures the control of the digital detector. The detector and the board are arranged in a casing which ensures their mechanical protection.
The cassette which is used in a portable system is subjected to far more handling than in a fixed radiological system, and its mechanical protection must be reinforced, notably in relation to impacts to which the cassette may be subjected during its displacements. More specifically, the digital detector is often made from photosensitive components which are arranged on a matrix on a glass plate which forms the most fragile element of the cassette. In addition to the impacts which could damage it, this plate is also sensitive to deformations, notably in the form of torsion.
The mechanical stresses which the cassette must withstand, and notably the digital detector, make it necessary to reinforce the structure of the casing, which is necessarily carried out to the detriment of the weight of the cassette.
In addition, the implementation of a radiological cassette involves particular stresses concerning thermal aspects. It has become apparent that the operation of the detector is adversely affected by the ambient temperature. It is possible to correct this adverse effect, for example by measuring the ambient temperature and correcting globally the image obtained from the detector. However, the presence of the electronic board in the casing of the cassette in the immediate vicinity of the detector may give rise to local effects in the radiological image. Firstly, the electronic board does not cover all of the surface of the detector. The area of the detector which faces the electronic board is therefore more affected thermally than the remainder of the detector. Secondly, locally in the electronic board, temperature differences may exist because of the presence of various components, the thermal dissipation of which can vary in large proportions. It then becomes difficult to correct the effects of these temperature differences.